Regenerative sustainer voltage generator

ABSTRACT

There is disclosed an improved sustaining voltage supply system for driving a gas discharge display panel having row-column conductor arrays, the matrix cross points of which are nonconductively coupled to a gaseous discharge medium in the panel. A pair of non-saturating transistor amplifier circuits are series connected and have the intermediate point thereof connected to supply the sustainer voltage to the panel. Each non-saturating amplifier circuit is provided with a regenerative feedback circuit. The feedback voltage is proportional to the load current during the &#39;&#39;&#39;&#39;on&#39;&#39;&#39;&#39; portion of its cycle. When the &#39;&#39;&#39;&#39;off&#39;&#39;&#39;&#39; portion of its cycle is reached, the feedback circuit is disabled.

United States Patent 1191 Leuck [451 Aug. 21, 1973 1 REGENERATIVE SUSTAINER VOLTAGE GENERATOR [52] US. Cl. 307/149, 340/324 R [51] Int. Cl. G06k 15/18 [58] Field of Search 307/106, 149, 108,

Primary Examiner-J. V. Truhe Assistant Examiner-M. Ginsburg Attorney-Donald K. Wedding et a1.

[57] ABSTRACT There is disclosed an improved sustaining voltage supply system for driving a gas discharge display panel having row-column conductor arrays, the matrix cross points of which are non-conductively coupled to a gaseous discharge medium in the panel, A pair of nonsaturating transistor amplifier circuits are series connected and have the intermediate point thereof connected to supply the'sustainer voltage to the panel.

[56] References Cited Each non-saturtatigg) ar}'1(p1ifier tcir1 :l:1itfis girjovifedlwith UNITED STATES PATENTS a regeneratlve ee ac circui e ee ac v2 tage 1s proportional to the load current during the on pori; 31 tion of its cycle. When the off portion of its cycle is 1 zer e a. 3,618,071 11 1971 Johnson et a1... 340 324 reached feedback c'rcult dlsabled' 3,281,704 10/1966 Crain 330/26 6 Claims, 3 Drawing Figures 44 REGENERATIVE FEEDBACK CIRCUIT 6' U 4a 46 /80 P C E NON-SATURATI' NG av PASS TRANSISTOR CIRCUIT DE TO 4,3 SELECTION MATRIX t f 42 8/ i PANEL I I 4.9 47 l\ PC 2 NON SATURATING BY PASS P TRANSISTOR CIRCUIT DIODE 45 REGENERATIVE FEEDBACK CIRCUIT Patented Aug. 21, 1973 2 Sheets-Sheet l Z v s 20 l3-l l7 l6 ROW 2 CONDUCTOR. l5

SELECTION MATRJX l3-N J COLUMN CONDUCTOR. 2/ SELECTlON MATRJX 32 SUSTAINER. CONTROL .3/

cmcun' 44 REGENERATIVE FEEDBACK CIRCUIT P c S NON-SATURATING av PASS TRANSISTOR CIRCUIT DIODE TO 43 SELECTION MATRIX a f 4 42 8/ .L PANEL U .9 47 33 PC ow SATU RATING BY PAss s TRANSISTOR CIRCUIT DIODE I 45 REGENERATIVE FEEDBACK cmcun' Patented Aug. 21, 1973 2 Sheets-Sheet 2 GLOW VOLTAGE GLOW VOLTAGE REGENERATIVE SUSTAINER VOLTAGE GENERATOR The present invention is directed to a sustaining voltage supply system which is particularly and uniquely designed for driving gaseous discharge display panels of the type disclosed in Baker et al. U.S. Pat. No..

3,499,167. Sustaining voltage generators constituting such systems supply operating power to gaseous discharge devices wherein the cross conductor arrays, e.g., the row and column conductors are dielectrically isolated from the discharge medium so as to not be in conductive contact therewith and the load on the generator is essentially capacitive in nature. Thus, some aspects of instant design are dictated by power and voltage frequency requirements of the panel, the frequency being in the range of about 30-50 kI-Iz. Because of the nonlinearity of the impedance presented by the panel to the generator, and the pulsing nature of the discharges in the panel so that the load currents are pulsing in nature, distortion in the sustaining voltage waveform can effect the operating characteristics of the device to such an extent as to distort and disturb the memory function thereof.

Accordingly, the present invention is directed to a high power, square wave sustaining voltage generators for gas discharge display panels having lower distortion in the waveform of the sustainer voltage as applied to the panel. As used herein, notching or notch distortion means the distortion in the sustainer voltage waveform caused by the firing of a large number of discrete sites in the display panel as served by a common sustaining generator. According to the invention, a pair of nonsaturating transistor amplifiers are connected in series across a supply voltage source with the intermediate point between the two transistor amplifiers being connected to the conductor arrays of the panel via any addressing and/or multiplexing circuit. Each such amplifier is provided with a regenerative feedback circuit, the feedback voltage being proportional to the load current.

In addition the non-conductive transistor is maintained off. High power square wave sustainer voltage generators constructed according to the present invention do not spike-short circuit the power supply, thereby reducing power requirements, reducing heat dissipation and operates with essentially zero store time.

BRIEF DESCRIPTION OF THE DRAWINGS i Theabove and other objects, advantages and fea tures of the invention will become more apparent in light of the following specification taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a diagrammatic illustration of the gaseous discharge display panel to which the invention has been applied.

FIG. 2 is a simplified block diagram for illustrating the principles of the invention,

FIG. 3 is a circuit diagram illustrating details of a sustaining voltage generator incorporating the invention Referring to FIG. 1, the gaseous discharge display panel is generally of the type disclosed in Baker et al. U.S. Pat. No. 3,499,167 and is constituted by a pair of support plates 11 and 12 on which are placed row conductor array 13 and column conductor array 14, the conductor arrays having dielectric or insulating coatings l5 and 16 applied thereto so that there is no conductive current passing from the conductors via the dielectric coating to the gaseous medium, that is, the matrix cross points defined by the cross conductor arrays are non-conductively coupled to the gaseous discharge medium in the panel. The respective plates are joined in spaced apart relation by a spacer sealant means 17 to form a thin gaseous discharge chamber which may be placed a neon-argon gas mixture (99.9 percent neon and 0.1 percent argon is preferred) as is disclosed in Nolan application, Ser. No. 764,577 filed Oct. 2, 1968. Other gaseous discharge mediums may likewise be incorporated in the panel but the improvement achieved by the use of the gas mixture recited above permits the panels to be operated in the 30-50 kHz range without being damaged by thermal shock and at the same time with good light output and good memory margins. The dielectric or insulative layers 15 and 16 may be treated with a lead oxide coating (not shown) to lower the operating voltage level.

The individual conductors in row conductor array 13 are preferably driven by row conductor selection matrix 20 and the column conductors are preferably driven by column conductor selection matrix 21, such selection matrices not forming a part of the present invention but may be constituted by diode-resistor selection matrices, multiplexed or non-multiplexed as may be desired. However, instead of a selection matrix operating on multiplex principles, individual pulsing circuits may be used for selecting individual ones of the row and column conductors, respectively. The selection matrices 20 and 21 receive input signals from a signal source, not shown, but which may be a computer, keyset, tape reader or other data source.

A pair of sustaining generator voltage sources 30 and 31 are provided for supplying opposite phase or opposite polarity sustaining potentials to the row conductor array 13 and the column conductor array 14 in the panel 10.

Essentially, one-half of the sustainer potential as applied to the panel is applied to row conductors and the other one-half of the sustainer potential is applied to the column conductors it being noted that the sustaining generators 30 and 31 have a common point or terminal G (which is not necessarily electrical ground) so that in the arrangement shown, the potentials generated in or produced by row conductor selection matrix 20 floats or is referenced to the potential from the sustanier generator source 30 and similarly the firing and discharge condition manipulating potentials generated in the column conductor selection matrix are in series with and have as a reference point the instantaneous voltage from sustaining generator 31 Moreover, both sustaining generators 30 and 31 receive controlling logic input signals from a source 32 which if desired, may be a multivibrator or other signal source, such as a computer. Thus, it may be desirable at times to erase the panel in which case one of the signals applied to one of the sustainer generators 30 and 31 may simply be removed for a certain time interval to thereby permit bulk erasing of all information on the panel or it may be desirable to vary the sustaining rate by varying the sustaining rate from control circuit 32.

Referring now to the block diagram FIG. 2, a sustaining voltage generator in accordance with the present invention is essentially constituted by a pair of nonsaturating transistor circuits 41 and 42 which have an intermediate point 43 therebetween which is connected via the matricing circuits shown in FIG. 1 to the respective row or column conductors on the panel. A capacitance Cp is diagrammatically illustrated as being connected to the intermediate point 43 as the equivalent panel capacitance. lt will be appreciated that this capacitance is the panel capacitance per se and is not necessarily present as a discrete capacitance element.

Each non-saturating transistor circuits 41 and 42 has its own regenerative feedback circuit 44 and 45 respectively with their respective outputs being applied to the input circuits of the non-saturating transistor circuit via summing points or circuits 46 and 47, respectively, along with the logic or control signal voltages from coupler circuits 48 and 49 respectively. In addition, bypass diode circuit 80 furnishes a return path for return currents when the generator on the opposite side has reversed, e.g., when generator 31 reverses the corresponding diode 80 means in generator 30 provides a return path for the panel displacement current.

Referring now to FIG. 3, one sustaining generator for one of the conductor arrays is shown in detail, it being appreciated that the conductor in the arrays may be sectioned or grouped with a sustainer generator for each section or group of conductors on the panel. The input sustainer control signals S and S (FIG. 1) are shown as being applied from a logic source (sustainer control logic 32, FIG. 1) by way of transformers T1 and T2 with the ground connection GL being the ground or reference of the applied logic signals. The upper half of the circuit is essentially the same as the lower half and will therefore be described in detail. Initially, it will be noted that the signals developed in the secondary of transformer T1 are applied by way of decoupling resistors 40 and 41 to the bases of transistors 42 and 73 respectively. Transistor 42 is coupled by way of a resistor 44 and bypass or speedup capacitor 45 to the base of transistor 46 with a connection by way of resistor 47 to the high voltage supply Vcc. The collector of transistor 46 is connected to a voltage divider consititued by resistors 48 and 49, respectively with the intermediate point 50 of the voltage divider being connected by way of disconnect or clamp diode 51. The cathode of diode 51 is connected to the base of transistor 52, with the output of transistor 52 being supplied to the base of transistor 53 by way of a small resistor 54. The collector of transistor 52 is connected by a turn-off resistor 56 to the output terminal 43 of the circuit.

Transistor 53 is connected as an emitter follower transistor and in such a way as to not saturate. A very small ohmic value resistor 57 is connected in the collector circuit of transistor 53. Resistor 57 is in a regenerative feedback loop which includes the driver transistor 52, and resistor 58 and conductor 59.

Transistor 73 is a phase inverter transistor, connected to the Vcc supply through resistor 74, and, which has its output coupled by way of a speed up resistor-capacitor circuit 60 to the base of transistor 61. The collector of transistor 61 is connected through resistor 62 to the base of transistor 52. In operation, a pulse voltage on transformer Tls primary is coupled over and induced into secondary of transformer T1 and applied simultaneously to the bases of transistors 42 and 73. Thus, when a positive voltage (for example) is induced in the secondary of transformer T1, this positive voltage, applied to the bases of transistors 42 and 73 will be inverted by phase inverter transistor 73, applied to the base of transistor 61. The output of transistor 61 is coupled through resistor 62 and turns on driver transistor 52. Driver transistor 52, in turn, initiates a flow of current through emitter follower transistor 53 and feedback resistor 57. Thus, the current to the load passes in this series circuit through the regenerative feedback resistor 57 and the voltage developed across this resistor is applied to the base-emitter circuit of transistor 52 for controlling the conduction condition of transistor 53. It will be appreciated that this feedback voltage is thereby directly proportional to the load current.

Diode 51 is for the purpose of disabling the feedback circuit whenever the control signal developed at transformer T1 is removed. It will be noted that when the positive pulse signal developed at transformer T1 secondary is applied to the base of transistor 42, this transistor applies its output to the base of transistor 46 which turns this transistor on to thereby connect the full Vcc potentials to the anode diode 51 to thereby back bias clamp diode 51. On removal of the control signal from the base of transistor 42, transistor 46 is rendered non-conductive to thereby assure that the voltage at intermediate point 50, even though there is a difi'erence in potential at the ends of series diode circuit 70, is sufficient to forward bias the diode 51 and thereby is sufficient to disable the feedback loop from feedback resistor 57.

Diode is provided for the purpose of furnishing return paths for return current when the generator on the opposite side of the panel 10 is reversed. if this diode were not present the charge at the panel or load could hold transistor 53 on by way of resistor 56. Diode 81 is used in the general case when an out of phase system may be applied to the panel.

The fact that the feedback'voltage is directly proportional to load current is a characteristic feature of the invention because as more discharge sites of the panel are turned on, there will be a heavier current to a load and hence a heavier positive feedback. it will be noted that the lower half of the circuit is substantially identical to the upper half except for the absence of the phase inverter transistor 73 in the lower half of the circuit. As indicated eariler, the logic pulse S applied to transformer T2 constitutes the pull down pulse input S is nested inside the pull up pulse applied to transfonner TI. This provides guard bands on each side logic signal S which assures that the pull up and pull down are never turned on at the same time. It will be appreciated that instead of transformers the pull up and pull down could be four separate logic inputs. The use of the inverter transistor 73 eliminates the need for the second set of inputs. It will be appreciated that the logic or control signal voltages applied to transformers T1 and T2 can be variable in order to vary the timing and hencethe width of the sustainer voltage square wave forms. The basic feature of the invention is in the use of a small resistor 57 in a positive or regenerative feedback loop with a driver transistor 52 and emitter follower transistor 53 to supply square wave sustainer voltages to the panel.

It will be apparent that many modifications and adaptations of the invention will be apparent to those skilled in the art and it is intend to encompass such obvious modifications and changes in the scope of the claims appended hereto.

What is claimed is:

l. A sustainer voltage supply system for a gas discharge display panel having row-column conductor arrays, the matrix cross-points of which are nonconductively coupled to a gas discharge medium in the panel comprising a pair of sustainer voltage generator means, one for the row conductor array and one for the column conductor array, each said sustainer generator means including,

a pair of separately switchable alternately on-off nonsaturating transistor amplifiers including input and output circuits therefor, means connecting said amplifiers in series circuit and providing an intermediate point between said transistor amplifiers,

means connecting said intermediate point between said non-saturating transistor amplifiers to the conductors in an array,

regenerative feedback circuit means including means for generating a positive feedback voltage, one regenerative feedback circuit means for each of said non-saturating transistor amplifier for supplying said positive feedback voltage to its respective nonsaturating transistor amplifier from the output circuit to the input circuit, and

control means supplying a control signal connected to the respective input circuits of said nonsaturating transistor amplifiers for alternately controlling the conduction conditions thereof.

2. The invention defined in claim 1, the means for generating a positive feedback voltage for each said regenerative feedback circuit means includes a low ohmic value impedance in series circuit whereby the load current flows therethrough and the feedback voltage is proportional to said load current.

3. The invention in claim 1 each non-saturating amplifier including low ohmic value resistor between said intermediate point and the base of said non-saturating transistor amplifier to reduce the fall time.

4. The invention in claim 3 including means for disabling said regenerative feedback circuit means when said control signal to said non-saturating amplifier from said control means is removed.

5. The invention defined in claim 1 wherein there is a control means for each non-saturating amplifiers and amplifier, respectively.

each said control means includes a control amplifier for supplying a control signal to said transistor amplifier and a diode clamp means for disabling said feedback circuit means when said control signal from said control amplifier is removed.

6. In a system for supplying square wave sustaining potentials to a pair of transversely related conductor arrays in a capacitive load type gas discharge panel wherein the crossing points of said conductor arrays locates a plurality of discharge sites in the panel, direct current high voltage source having a pair of output terminals one of which constitutes a point of reference potential, a first pair of controllable impedance means connected in a series circuit across said high voltage source and having a point intermediate said first controllable impedance means connected to one of said conductor arrays, a second pair of controllable impedance means connected in series across said high voltage source in the same polarity in a direction opposite said first pair of controllable impedance means and a point intermediate said second pair of controllable impedance means being connected to the other one of said conductor arrays, an impedance control means for alternately controlling rapid impedance lowering and rapid impedance raising of said controllable impedance means at selected times such that said high voltage source is first connected to said conductor arrays, respectively, to supply charging current thereto and secondly to said point of reference potential to discharge said conductor arrays, the improvement comprising each of said controllable impedance means being constituted by at least one non-saturating transistor amplifier circuit, each non-saturating transistor amplifier having an input circuit' and an output circuit, said impedance control means including a separate control circuit for each non-saturating transistor amplifier circuit to control the time duration of each square wave potential, means connecting each said control circuit to receive a low level logic voltage from a source thereof and a regenerative feedback circuit between the input and output circuits of each non-saturating transistor 

1. A sustainer voltage supply system for a gas discharge display panel having row-column conductor arrays, the matrix cross-points of which are non-conductively coupled to a gas discharge medium in the panel comprising a pair of sustainer voltage generator means, one for the row conductor array and one for the column conductor array, each said sustainer generator means including, a pair of separately switchable alternately on-off nonsaturating transistor amplifiers including input and output circuits therefor, means connecting said amplifiers in series circuit and providing an intermediate point between said transistor amplifiers, means connecting said intermediate point between said nonsaturating transistor amplifiers to the conductors in an array, regenerative feedback circuit means including means for generating a positive feedback voltage, one regenerative feedback circuit means for each of said non-saturating transistor amplifier for supplying said positive feedback voltage to its respective non-saturating transistor amplifier from the output circuit to the input circuit, and control means supplying a control signal connected to the respective input circuits of said non-saturating transistor amplifiers for alternately controlling the conduction conditions thereof.
 2. The invention defined in claim 1, the means for generating a positive feedback voltage for each said regenerative feedback circuit means includes a low ohmic value impedance in series circuit whereby the load current flows therethrough and the feedback voltage is proportional to said load current.
 3. The invention in claim 1 each non-saturating amplifier including low ohmic value resistor between said intermediate point and the base of said non-saturating transistor amplifier to reduce the fall time.
 4. The invention in claim 3 including means for disabling said regenerative feedback circuit means when said control signal to said non-saturating amplifier from said control means is removed.
 5. The invention defined in claim 1 wherein there is a control means for each non-saturating amplifiers and each said control means includes a control amplifier for supplying a control signal to said transistor amplifier and a diode clamp means for disabling said feedback circuit means when said control signal from said control amplifier is removed.
 6. In a system for supplying square wave sustaining potentials to a pair of transversely related conductor arrays in a capacitive load type gas discharge panel wherein the crossing points of said conductor arrays locates a plurality of discharge sites in the panel, direct current high voltage source having a pair of output terminals one of which constitutes a point of reference potential, a first pair of controllable impedance means connected in a series circuit across said high voltage source and having a point intermediate said first controllable impedance means connected to one of said conductor arrays, a second pair of controllable impedance means connected in series across said high voltage source in the same polarity in a direction opposite said first pair of controllable impedance means and a point intermediate said second pair of controllable impedance means being connected to the other one of said conductor arrays, an impedance control means for alternately controlling rapid impedance lowering and rapid impedance raising of said controllable impedance means at selected times such that said high voltage source is first connected to said conductor arrays, respectively, to supply charging current thereto and secondly to said point of reference potential to discharge said conductor arrays, the improvement comprising each of said controllable impedance means being constituted by at least one non-saturating transistor amplifier circuit, each non-saturating transistor amplifier having an input circuit and an output circuit, said impedance control means including a separate control circuit for each non-saturating transistor amplifier circuit to control the time duration of each square wave potential, means connecting each said control circuit to receive a low level logic voltage from a source thereof and a regenerative feedback circuit between the input and output circuits of each non-saturating transistor amplifier, respectively. 